In the developing of films such as x-ray and photographic films, it is known to utilize a series of treatment fluids, for developing, fixing, washing, and possibly still other treatment steps.
When automatic machinery is used for such film developing, these treatment fluids are usually placed in a series of tanks, through which the films being developed are then transported, by means of transport roller racks extending down into these tanks.
During operation of such automatic film developing machines the fluids in the tanks gradually become depleted, and must therefore be replenished. Generally, the treatment fluid in any given tank consists of a mixture of chemicals and water. For proper replenishment, there must be maintained not only the overall fluid level in the tank, but also the relative concentration of the chemicals. This replenishing requirement has heretofore not been completely satisfactorily met. The prevailing technique for replenishing involves pouring the replenisher ingredients--the chemicals--into a container, stirring these chemicals in the container, and then pouring the resultant mixture into the tank, in quantities and at intervals such as to maintain in the tank the desired level and proportions of chemicals.
It is known to automate certain aspects of this technique. For example, our prior U.S. Pat. No. 3,752,052, issued Aug. 14, 1973, teaches automatic control of a pump which delivers replenisher fluid to the machine treatment tank as needed.
What is not disclosed in this prior patent is how to obtain initially the correct replenisher fluid mixture, which the pump can then automatically deliver to the developing machine.
There are a wide variety of mixtures which are used for replenishment in film developing. For example, a replenisher for the developer fluid may consist of a developing agent (such as sold by Kodak under the commercial name Elon), anhydrous sodium sulfite, monohydrate sodium carbonate, and sodium hydroxide in aqueous solution.
Many other ingredients and proportions are possible.
Although for some of these mixtures the chemicals are available from manufacturers in premixed form, these are generally impractical for modern, high-speed automatic developing machines because of the high cost of such premixed chemicals. As a practical matter it is therefore necessary to acquire the individual chemicals in separate bulk containers, and to mix them at the site of the machine. In any event, the water is admixed on site since it determines the concentration of the final replenisher mixture, which must be adjusted locally in accordance with current operating conditions.
This on-site mixing, by the prevailing technique previously described, is accompanied by undesirable side effects.
There is fluid waste in pouring into and out of the container in which the mixing is performed. Some of the fluids used are quite "messy", leading to unsightly premises where the mixing takes place and sometimes even to conditions which are potentially hazardous to health and property.
The mixture itself suffered from the fact that the ingredients are generally quite difficult to blend homogeneously and uniformly unless vigorously stirred. Moreover, this stirring sometimes had to be repeated at frequent intervals to overcome the tendency of the chemicals to reseparate. This in turn further accentuated the other problems of spillage previously described.
Finally, over a period of time the chemicals of the replenisher mixtures may react with each other, and/or may be oxidized by the air which has access into the mixture both during the stirring and also later, as portions of the mixture in the container are gradually emptied into the machine. This caused deterioration of the replenisher mixtures formed by the prevailing technique under discussion.
While these problems occur primarily in the film developing industries, in other industries, typically chemical or biochemical, where the system of the invention can also be used, as explained hereinafter, similar difficult problems exist caused by the lack of equipment capable of mixing or blending difficult to mix components.